U.S. patent application number 12/899032 was filed with the patent office on 2011-04-07 for apparatus and method for transmitting/receiving signal in wireless communication system.
This patent application is currently assigned to PANTECH CO., LTD.. Invention is credited to Kyoungmin PARK, Sung-jin SUH.
Application Number | 20110081933 12/899032 |
Document ID | / |
Family ID | 43823586 |
Filed Date | 2011-04-07 |
United States Patent
Application |
20110081933 |
Kind Code |
A1 |
SUH; Sung-jin ; et
al. |
April 7, 2011 |
APPARATUS AND METHOD FOR TRANSMITTING/RECEIVING SIGNAL IN WIRELESS
COMMUNICATION SYSTEM
Abstract
Disclosed are apparatuses and methods for signal
transmission/reception between a user equipment (UE) and a base
station (BS) or cell in a wireless communication system in which a
position of a US may be determined by identifying according to a
positioning reference signal (PRS) pattern. By a method of
transmitting PRSs using a more effective and efficient muting
method, it is possible to reduce interference between multiple base
stations that simultaneously transmit a same PRS pattern.
Inventors: |
SUH; Sung-jin; (Seoul,
KR) ; PARK; Kyoungmin; (Goyang-si, KR) |
Assignee: |
PANTECH CO., LTD.
Seoul
KR
|
Family ID: |
43823586 |
Appl. No.: |
12/899032 |
Filed: |
October 6, 2010 |
Current U.S.
Class: |
455/509 |
Current CPC
Class: |
G01S 5/0236 20130101;
H04B 17/27 20150115; G01S 5/10 20130101; H04W 64/00 20130101; H04B
17/364 20150115 |
Class at
Publication: |
455/509 |
International
Class: |
H04B 7/00 20060101
H04B007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Oct 6, 2009 |
KR |
10-2009-0094869 |
Claims
1. A method for signal communication of a wireless communication
system, the method comprising: allocating N consecutive downlink
subframes for a positioning reference signal (PRS) to each period
of a plurality of periods for at least one base station, the PRS
being allocated as large as a PRS bandwidth of a total bandwidth;
by the at least one base station, transmitting the PRS or muting
the PRS to a terminal in the N consecutive downlink subframes of at
least one period of the plurality of periods; by the terminal,
receiving at least one of the transmitted PRS or the muted PRS from
the at least one base station in the N consecutive downlink
subframes of the at least one period of the plurality of periods;
and by the terminal, calculating at least one difference of arrival
time of the transmitted PRS or the muted PRS from the at least one
base station wherein the N, the PRS bandwidth, and the period of
the at least one base station are delivered to the terminal from
the at least one base station; and wherein transmitting the PRS or
muting the PRS comprises transmitting all PRS or muting all PRS in
the N consecutive downlink subframes of the at least one period of
the plurality of periods.
2. The method of claim 1, wherein the N consecutive downlink
subframes comprise one of 2, 4, or 6 consecutive downlink
subframes.
3. The method of claim 1, wherein each period comprises one of 160
ms, 320 ms, 640 ms, or 1280 ms.
4. The method of claim 1, wherein the transmitting or muting
further comprises: transmitting the PRS in the N consecutive
downlink subframes or muting the PRS in the N consecutive downlink
subframes according to a normal cyclic prefix length or an extended
cyclic prefix length.
5. The method of claim 1, wherein the allocating further comprises:
allocating normal subframes configured for PRS transmission and
multicast broadcast single frequency network (MBSFN) subframes
configured for PRS transmission to the N consecutive downlink
subframes.
6. The method of claim 1, wherein the PRS are not mapped to
resource elements allocated to a physical broadcast channel (PBCH),
a primary synchronization signal (PSS), or a secondary
synchronization signal (SSS).
7. The method of claim 1, wherein the base station transmits a PRS
according to a specific PRS pattern.
8. The method of claim 1, wherein the N, the PRS bandwidth, and the
period of the at least one base station are configured by higher
layer of the base station.
9. A method for signal transmission of a wireless communication
system, the method comprising: allocating N consecutive downlink
subframes for a positioning reference signal (PRS) to each period
of a plurality of periods for at least one base station, the PRS
being allocated as large as a PRS bandwidth of a total bandwidth;
and by the at least one base station, transmitting the PRS or
muting the PRS to a terminal in the N consecutive downlink
subframes of at least one period of the plurality of periods;
wherein the N, the PRS bandwidth, and the period of the at least
one base station are delivered to the terminal from the at least
one base station; and wherein transmitting the PRS or muting the
PRS comprises transmitting all PRS or muting all PRS in the N
consecutive downlink subframes of the at least one period of the
plurality of periods.
10. The method of claim 9, wherein the N consecutive downlink
subframes comprise one of 2, 4, or 6 consecutive downlink
subframes.
11. The method of claim 9, wherein each period comprises one of 160
ms, 320 ms, 640 ms, or 1280 ms.
12. A method for signal receiving of a wireless communication
system, the method comprising: by the terminal, receiving at least
one of a transmitted positioning reference signal (PRS) or a muted
PRS in N consecutive downlink subframes of at least one period of a
plurality of periods from at least one base station, the PRS being
allocated as large as a PRS bandwidth of a total bandwidth; and by
the terminal, calculating at least one difference of arrival time
of the transmitted PRS or the muted PRS from the at least one base
station; wherein the N, the PRS bandwidth, and the period of the at
least one base station are delivered to the terminal from the at
least one base station; and wherein transmitting the PRS or muting
the PRS comprises transmitting all PRS or muting all PRS in the N
consecutive downlink subframes of the at least one period of the
plurality of periods.
13. The method of claim 12, wherein the N consecutive downlink
subframes comprise one of 2, 4, or 6 consecutive downlink
subframes.
14. The method of claim 12, wherein each period comprises one of
160 ms, 320 ms, 640 ms, or 1280 ms.
15. A wireless communication system, comprising: at least one base
station to allocate N consecutive downlink subframes for a
positioning reference signal (PRS) to each period of a plurality of
periods for at least one base station, the PRS being allocated as
large as a PRS bandwidth of a total bandwidth and transmit the PRS
or muting the PRS to a terminal in the N consecutive downlink
subframes of at least one period of the plurality of periods; and
the terminal to receive at least one of the transmitted PRS or the
muted PRS from the at least one base station in the N consecutive
downlink subframes of the at least one period of the plurality of
periods; and calculate at least one difference of arrival time of
the transmitted PRS or the muted PRS from the at least one base
station, wherein the N, the PRS bandwidth, and the period of the at
least one base station are delivered to the terminal from the at
least one base station; and wherein transmitting the PRS or muting
the PRS comprises transmitting all PRS or muting all PRS in the N
consecutive downlink subframes of the at least one period of the
plurality of periods.
16. The system of claim 15, wherein the N consecutive downlink
subframes comprise one of 2, 4, or 6 consecutive downlink
subframes.
17. The system of claim 15, wherein each period comprises one of
160 ms, 320 ms, 640 ms, or 1280 ms.
18. The system of claim 15, wherein the at least one base station
further transmits the PRS in the N consecutive downlink subframes
or muting the PRS in the N consecutive downlink subframes according
to a normal cyclic prefix length or an extended cyclic prefix
length.
19. The system of claim 15, wherein the at least one base station
further allocates normal subframes configured for PRS transmission
and multicast broadcast single frequency network (MBSFN) subframes
configured for PRS transmission to the N consecutive downlink
subframes.
20. The system of claim 15, wherein the PRS are not mapped to
resource elements allocated to a physical broadcast channel (PBCH),
a primary synchronization signal (PSS), or a secondary
synchronization signal (SSS).
21. The system of claim 15, wherein the at least one base station 1
transmits a PRS according to a specific PRS pattern.
22. The method of claim 15, wherein the N, the PRS bandwidth, and
the period of the at least one base station are configured by
higher layer of the base station.
23. A signal transmission apparatus, comprising: a resource element
mapper to map complex modulation symbols of each antenna port to a
corresponding resource element; and a position reference signal
(PRS) resource allocation unit to allocate N consecutive downlink
subframes for a positioning reference signal (PRS) to each period
of a plurality of periods for at least one base station, the PRS
being allocated as large as a PRS bandwidth of a total bandwidth;
and transmit the PRS or muting the PRS to a terminal in the N
consecutive downlink subframes of at least one period of the
plurality of periods, wherein the N, the PRS bandwidth, and the
period of the at least one base station are delivered to the
terminal from the at least one base station; and wherein
transmitting the PRS or muting the PRS comprises transmitting all
PRS or muting all PRS in the N consecutive downlink subframes of
the at least one period of the plurality of periods.
24. The signal transmission apparatus of claim 23, wherein the N
consecutive downlink subframes comprise one of 2, 4, or 6
consecutive downlink subframes.
25. The signal transmission apparatus of claim 23, wherein each
period comprises one of 160 ms, 320 ms, 640 ms, or 1280 ms.
26. A signal reception apparatus, comprising: a reception
processing unit to receive at least one of a transmitted
positioning reference signal (PRS) or a muted PRS in N consecutive
downlink subframes of at least one period of a plurality of periods
from at least one base station, the PRS being allocated as large as
a PRS bandwidth of a total bandwidth; and a control unit calculate
at least one difference of arrival time of the transmitted PRS or
the muted PRS from the at least one base station, wherein the N,
the PRS bandwidth, and the period of the at least one base station
are delivered to the terminal from the at least one base station;
and wherein transmitting the PRS or muting the PRS comprises
transmitting all PRS or muting all PRS in the N consecutive
downlink subframes of the at least one period of the plurality of
periods.
27. The signal reception apparatus of claim 26, wherein the N
consecutive downlink subframes comprise one of 2, 4, or 6
consecutive downlink subframes.
28. The signal reception apparatus of claim 26, wherein each period
comprises one of 160 ms, 320 ms, 640 ms, or 1280 ms.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from and the benefit under
35 U.S.C. .sctn.119(a) of Korean Patent Application No.
10-2009-0094869, filed on Oct. 6, 2009, which is hereby
incorporated by reference for all purposes as if fully set forth
herein.
BACKGROUND
[0002] 1. Field
[0003] Exemplary embodiments of the present invention relate to an
apparatus and a method for transmitting and receiving signals
between a User Equipment (UE) and a Base Station (BS) in a wireless
communication system.
[0004] 2. Discussion of the Background
[0005] In a WCDMA (Wideband Code Division Multiple Access) system,
positioning methods for various positioning services and for
providing location information for communication systems are
generally based on three types of methods, which include: 1) a cell
coverage-based positioning method; 2) an OTDOA-IPDL (Observed Time
Difference of Arrival-Idle Period Downlink) method; and 3) a
network assisted GPS (Global Positioning System) method. These
methods are complementary to each other rather than competitive to
each other, and are exploited properly for their own purposes,
respectively.
[0006] Among these three methods, the OTDOA (Observed Time
Difference of Arrival) method is based on a measurement of the
relative arrival time of reference signals, or pilot signals, from
different base stations or cells. For the calculation of a
location, a UE (User Equipment) or MS (Mobile Station) receives
reference signals (or pilot signal) from at least three different
base stations or cells. In addition, in order to make the OTDOA
positioning measurement easier and to avoid the near-far problem,
the WCDMA standards include IPDL (Idle Periods in Downlink). During
one Idle Period of the WCDMA standards, a UE (or MS) is required to
be capable of receiving a reference signal (or pilot signal) from
an adjacent base station or cell, even when a reference signal (or
pilot signal) transmitted with the same frequency bandwidth from a
current serving base station or serving cell to which the UE
currently belongs is strong.
[0007] The LTE (Long Term Evolution) system, which has been
developed from the WCDMA of the 3GPP (3.sup.rd Generation
Partnership Project), is based on the OFDM (Orthogonal Frequency
Division Multiplexing), which is different from the asynchronous
CDMA system of the WCDMA. As is in the current WCDMA system,
positioning based on the OTDOA method is considered in the new LTE
system also. To this end, current discussion for the LTE system
includes employment of a method in which a data region is punctured
with a certain period in a normal subframe and/or an MBSFN
(Multicast Broadcast Single Frequency Network) subframe, and a
reference signal for positioning (positioning reference signal) is
transmitted in the punctured area. That is, for positioning in the
LTE, which is a next-generation communication method, it is
necessary to reconsider a method for transmitting a positioning
reference signal and the construction of the positioning reference
signal in the new resource positioning structure, which has changed
communication bases, such as the multiplexing method and the access
method, although it is based on the OTDOA method in the existing
WCDMA. Further, the development of communication systems, including
an increasing speed in the movement of a UE, a changing
interference environment between base stations, and an increasing
complexity of the communication environment, requires a more exact
positioning method.
SUMMARY
[0008] Additional features of the invention will be set forth in
the description which follows, and in part will be apparent from
the description, or may be learned by practice of the
invention.
[0009] An exemplary embodiment of the present invention discloses a
method for signal communication of a wireless communication system,
the method including: allocating N consecutive downlink subframes
for a positioning reference signal (PRS) to each period of a
plurality of periods for at least one base station, the PRS being
allocated as large as a PRS bandwidth of a total bandwidth; by the
at least one base station, transmitting the PRS or muting the PRS
to a terminal in the N consecutive downlink subframes of at least
one period of the plurality of periods; by the terminal, receiving
at least one of the transmitted PRS or the muted PRS from the at
least one base station in the N consecutive downlink subframes of
the at least one period of the plurality of periods; and by the
terminal, calculating at least one difference of arrival time of
the transmitted PRS or the muted PRS from the at least one base
station, wherein the N, the PRS bandwidth, and the period of the at
least one base station are delivered to the terminal from the at
least one base station, and wherein transmitting the PRS or muting
the PRS includes transmitting all PRS or muting all PRS in the N
consecutive downlink subframes of the at least one period of the
plurality of periods.
[0010] An exemplary embodiment of the present invention discloses a
method for signal transmission of a wireless communication system,
the method including: allocating N consecutive downlink subframes
for a positioning reference signal (PRS) to each period of a
plurality of periods for at least one base station, the PRS being
allocated as large as a PRS bandwidth of a total bandwidth; and by
the at least one base station, transmitting the PRS or muting the
PRS to a terminal in the N consecutive downlink subframes of at
least one period of the plurality of periods, wherein the N, the
PRS bandwidth, and the period of the at least one base station are
delivered to the terminal from the at least one base station, and
wherein transmitting the PRS or muting the PRS includes
transmitting all PRS or muting all PRS in the N consecutive
downlink subframes of the at least one period of the plurality of
periods.
[0011] An exemplary embodiment of the present invention discloses a
method for signal receiving of a wireless communication system, the
method including: by the terminal, receiving at least one of a
transmitted positioning reference signal (PRS or a muted PRS in N
consecutive downlink subframes of at least one period of a
plurality of periods from at least one base station, the PRS being
allocated as large as a PRS bandwidth of a total bandwidth; and by
the terminal, calculating at least one difference of arrival time
of the transmitted PRS or the muted PRS from the at least one base
station, wherein the N, the PRS bandwidth, and the period of the at
least one base station are delivered to the terminal from the at
least one base station, and wherein transmitting the PRS or muting
the PRS includes transmitting all PRS or muting all PRS in
bandwidth in the N consecutive downlink subframes of the at least
one period of the plurality of periods.
[0012] An exemplary embodiment of the present invention discloses a
wireless communication system, including: at least one base station
to allocate N consecutive downlink subframes for a positioning
reference signal (PRS) to each period of a plurality of periods for
at least one base station and to transmit the PRS or mute the PRS
to a terminal in the N consecutive downlink subframes of at least
one period of the plurality of periods, the PRS being allocated as
large as a PRS bandwidth of a total bandwidth; and the terminal to
receive at least one of the transmitted PRS or the muted PRS in the
N consecutive downlink subframes of the at least one period of the
plurality of periods from the at least one base station and to
calculate at least one difference of arrival time of the
transmitted PRS or the muted PRS from the at least one base
station, wherein the N, the PRS bandwidth, and the period of the at
least one base station are delivered to the terminal from the at
least one base station, and wherein transmitting the PRS or muting
the PRS includes transmitting all PRS or muting all PRS in the N
consecutive downlink subframes of the at least one period of the
plurality of periods.
[0013] An exemplary embodiment of the present invention discloses a
signal transmission apparatus, including: a resource element mapper
to map complex modulation symbols of each antenna port to a
corresponding resource element; and a position reference signal
(PRS) resource allocation unit to allocate N consecutive downlink
subframes for a PRS to each period of a plurality of periods for at
least one base station; and to transmit the PRS or mute the PRS to
a terminal in the N consecutive downlink subframes of the at least
one period of the plurality of periods, the PRS being allocated as
large as a PRS bandwidth of a total bandwidth, wherein the N, the
PRS bandwidth, and the period of the at least one base station are
delivered to the terminal from the at least one base station, and
wherein transmitting the PRS or muting the PRS includes
transmitting all PRS or muting all PRS in the N consecutive
downlink subframes of the at least one period of the plurality of
periods.
[0014] An exemplary embodiment of the present invention discloses a
signal reception apparatus, including: a reception processing unit
to receive at least one of a transmitted positioning reference
signal (PRS) or a muted PRS in N consecutive downlink subframes of
at least one period of a plurality of periods from the at least one
base station, the PRS being allocated as large as a PRS bandwidth
of a total bandwidth; and a control unit to calculate at least one
difference of arrival time of the transmitted PRS or the muted PRS
from the at least one base station, wherein the N, the PRS
bandwidth, and the period of the at least one base station are
delivered to the terminal from the at least one base station, and
wherein transmitting the PRS or muting the PRS includes
transmitting all PRS or muting all PRS in the N consecutive
downlink subframes of the at least one period of the plurality of
periods.
[0015] It is to be understood that both the foregoing general
description and the following detailed description are exemplary
and explanatory and are intended to provide further explanation of
the invention as claimed.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] The accompanying drawings, which are included to provide a
further understanding of the invention and are incorporated in and
constitute a part of this specification, illustrate embodiments of
the invention, and together with the description serve to explain
the principles of the invention.
[0017] FIG. 1 is a block diagram illustrating a wireless
communication system according to an exemplary embodiment of the
present invention.
[0018] FIG. 2 and FIG. 3 illustrate patterns of positioning
reference signals tentatively determined in a current LTE system
for one subframe, when a normal CP (cyclic prefix) is added in a
normal subframe and when an extended CP is added in a normal
subframe, respectively.
[0019] FIG. 4 illustrates a transmission apparatus for generating
and transmitting a PRS pattern according to an exemplary embodiment
of the present invention.
[0020] FIGS. 5 to 10 illustrate methods of transmitting PRSs in
muting patterns for N and K according to exemplary embodiments of
the present invention.
[0021] FIG. 11 illustrates an arrangement of BSs (cells) divided
into three groups according to the muting pattern for transmission
of PRSs according to an exemplary embodiment of the present
invention.
[0022] FIG. 12 is a flowchart illustrating a method of positioning
of a UE according to an exemplary embodiment of the present
invention.
[0023] FIG. 13 is a block diagram illustrating a signal receiving
apparatus of a UE according to an exemplary embodiment of the
present invention.
DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS
[0024] Exemplary embodiments now will be described more fully
hereinafter with reference to the accompanying drawings, in which
exemplary embodiments are shown. This disclosure may, however, be
embodied in many different forms and should not be construed as
limited to the exemplary embodiments set forth therein. Rather,
these exemplary embodiments are provided so that this disclosure
will be thorough and complete, and will fully convey the scope of
this disclosure to those skilled in the art. Various changes,
modifications, and equivalents of the systems, apparatuses, and/or
methods described herein will likely suggest themselves to those of
ordinary skill in the art. Like elements, features, and structures
are denoted by like reference numerals throughout the drawings and
the detailed description, and the size and proportions of some
elements may be exaggerated in the drawings for clarity and
convenience.
[0025] In addition, terms, such as first, second, A, B, (a), (b) or
the like may be used herein when describing components of the
present invention. Each of these terminologies is not used to
define an essence, order or sequence of a corresponding component
but used merely to distinguish the corresponding component from
other component(s). It should be noted that if it is described in
the specification that one component is "connected," "coupled" or
"joined" to another component, a third component may be
"connected," "coupled," and "joined" between the first and second
components, although the first component may be directly connected,
coupled or joined to the second component.
[0026] Further, since terms, such as "including," "comprising," and
"having" mean that one or more corresponding components may exist
unless they are specifically described to the contrary, it shall be
construed that one or more other components can be included. All of
the terminologies containing one or more technical or scientific
terminologies have the same meanings that persons skilled in the
art understand ordinarily unless they are not defined otherwise. A
term ordinarily used like that defined by a dictionary shall be
construed that it has a meaning equal to that in the context of a
related description, and shall not be construed in an ideal or
excessively formal meaning unless it is clearly defined in the
present specification.
[0027] The present disclosure provides a system and a method for
signal transmission in a wireless communication system, which can
additionally identify base stations, which transmit positioning
reference signals with a same positioning reference signal pattern,
by identifying each subframe of transmitting the positioning
reference signal for each base station.
[0028] FIG. 1 is a block diagram illustrating a wireless
communication system according to an exemplary embodiment of the
present invention.
[0029] The wireless communication system is arranged in order to
provide various communication services, such as voice, packet data,
etc.
[0030] Referring to FIG. 1, a wireless communication system
includes a UE (User Equipment) 10 and a BS (Base Station) 20. The
UE 10 and the BS 20 use various power allocation methods as
described below.
[0031] As used herein, the UE 10 has an inclusive meaning referring
to a user terminal in a wireless communication, and should be
construed as a concept including not only a UE in WCDMA, LTE, HSPA
(High Speed Packet Access), etc. but also a UT (User Terminal), SS
(Subscriber Station), and wireless device and an MS (Mobile
Station) in GSM (Global System for Mobile Communication).
[0032] The BS 20 may be a cell and generally refers to a fixed
station communicating with the UE 10, and may be called by another
name, such as Node-B, eNB (evolved Node-B), BTS (Base Transceiver
System), or AP (Access Point).
[0033] That is, as used herein, the BS 20 should be construed as
having an inclusive meaning indicating an area covered by a BSC
(Base Station Controller) of the CDMA, a Node B of the WCDMA, etc.,
and may correspond to one of various coverage areas, which include
a mega cell, a macro cell, a micro cell, a pico cell, femto cell,
etc.
[0034] The UE 10 and the BS 20 are not limited to specifically
expressed terms or words and inclusively indicate two transmitting
and receiving agents used for implementation of the technology
described herein.
[0035] There is no limit in the multiple access methods applicable
to a wireless communication system. That is, various multiple
access methods, such as CDMA (Code Division Multiple Access), TDMA
(Time Division Multiple Access), FDMA (Frequency Division Multiple
Access), OFDMA (Orthogonal Frequency Division Multiple Access),
OFDM-FDMA, OFDM-TDMA, and OFDM-CDMA, can be applied to the wireless
communication system. For example, the wireless communication
system may be an OFDM-based wireless communication system, which
includes at least one BS and at least one UE, wherein each of the
BS and the UE may include at least one antenna.
[0036] For uplink transmission and downlink transmission, it is
possible to use either a TDD (Time Division Duplex) method using
different times for transmission or an FDD (Frequency Division
Duplex) method using different frequencies for transmission.
[0037] Exemplary embodiments of the present invention can be
applied to resource allocation in the asynchronous wireless
communication, which is evolving to the LTE (Long Term Evolution)
and the LTE-A (LTE-advanced) through the GSM, the WCDMA, and the
HSPA, and resource allocation in the synchronous wireless
communication, which is evolving to the CDMA, the CDMA-2000, and
the UMB. Aspects of the present invention shall not be
restrictively construed based on a particular wireless
communication field and shall be construed to include all technical
fields.
[0038] FIG. 2 and FIG. 3 illustrate patterns of positioning
reference signals tentatively determined in a current LTE system
for one subframe, when a normal CP (cyclic prefix) is added in a
normal subframe and when an extended CP is added in a normal
subframe, respectively.
[0039] A basic positioning reference signal pattern is formed in a
1/2 resource block configured by two slots and six subcarriers
according to a particular sequence. An example of the used
particular sequence is {0, 1, 2, 3, 4, 5}. Further, the two slots
in the 1/2 resource block correspond to two time slots included in
a subframe for positioning (i.e., a positioning subframe). Now, a
method for forming a basic positioning reference signal pattern by
the particular sequence will be described.
[0040] When the particular sequence is given as
f(i)={f(0), f(1), f(2), f(3), f(4), f(5)}={0, 1, 2, 3, 4, 5}, a
positioning reference signal is formed at a subcarrier position in
the frequency domain corresponding to the first value of the
sequence from the last symbol in each of the two slots. That is, in
the case of the last symbol, since the first value of the sequence
is 0, a positioning reference signal is formed at the 0th
subcarrier position. Next, in the second symbol from the last, a
positioning reference signal is formed at the subcarrier position
on the frequency domain corresponding to the second value of the
sequence. That is, in the case of the second symbol from the last,
since the second value of the sequence is 1, a positioning
reference signal is formed at the 1st subcarrier position. In the
same manner, positioning reference signals are formed at subcarrier
positions in the frequency domain corresponding to sequence values
up to the sixth symbol from the last in each of the two slots.
[0041] Referring to FIG. 3, in the generated positioning reference
signal pattern, the control regions, such as PDCCH (Physical
Downlink Control Channel), PHICH (Physical Hybrid-ARQ Indicator
Channel), and PCFICH (Physical Control Format Indicator Channel),
the symbol axis in which CRSs (Cell-specific Reference Signals)
exist, and REs (Reference elements) in which PSSs (Primary
Synchronization Signals), SSSs (Secondary Synchronization Signals),
and BCHs (Broadcast Channels) exist, are punctured so that they are
excluded from the basic positioning reference signal pattern.
[0042] The process of forming the basic positioning reference
signal pattern as described above can be expressed by the following
equations.
[0043] If .nu. is a value for defining positions of different
Positioning Reference Signals (PRSs) in the frequency domain and
the total number of OFDM symbols in each slot in the downlink is
N.sub.symb.sup.DL, a basic positioning reference signal pattern for
a corresponding 1.sup.st OFDM symbol in each slot is formed
according to Equation (1) defined below.
v = 5 - l + N CP l = N symb DL - i for i = 1 , 2 , 4 , , 4 + ( n 5
mod 2 ) + N CP N CP = { 1 for normal CP 0 for extended CP ( 1 )
##EQU00001##
[0044] In Equation (1), N.sub.symb.sup.DL has a value of 7 for a
normal CP or 6 for an extended CP, and (n, mod 2) has a value of 0
for an even slot or 1 for an odd slot. Therefore, from equation
(1), l can be defined by
l = { 2 , 3 , 5 , 6 if n 5 mod 2 = 0 and N CP = 1 1 , 2 , 3 , 5 , 6
if n 5 mod 2 = 1 and N CP = 1 2 , 4 , 5 if n 5 mod 2 = 0 and N CP =
0 1 , 2 , 4 , 5 if n 5 mod 2 = 1 and N CP = 0. ##EQU00002##
[0045] The basic positioning reference signals formed in the 1/2
resource block including six subcarriers and two slots configuring
one subframe are allocated up to the system bandwidth along the
frequency axis and allocated to N subframes repeatedly with a
particular period along the time axis.
[0046] For example, if the system bandwidth is 10 Mhz, the
frequency axis includes a total of 50 Resource Blocks (RBs).
Therefore, the basic positioning reference signal pattern formed in
the 1/2 Resource Block (RB) is repeated 100 times along the
frequency axis. If the total number of RBs corresponding to the
downlink system bandwidth is N.sub.RB.sup.DL, the basic positioning
reference signal pattern is repeated 2N.sub.RB.sup.DL times in
total.
[0047] When the basic positioning reference signals are allocated
to N subframes repeatedly with a particular period along the time
axis, the basic positioning reference signals are distributed in a
time-varying manner depending on the Subframe Number (SFN) and the
cell-specific information of each cell, such as PCI (Physical Cell
Identity), differently from the frequency axis. To this end, by
using .nu. as a value for defining positions of the different
positioning reference signals in the frequency domain according to
the SFN and the cell-specific information, and using .nu..sub.shift
as a value corresponding to the variance shifted along the
frequency axis, the positions of the subcarriers, in which the PRSs
are formed in each symbol, are equally cyclic-shifted by
.nu..sub.shift.
[0048] For the k.sup.th subcarrier in the entire system bandwidth
including N.sub.RB.sup.DLN.sub.sc.sup.RB subcarriers, the
above-described process can be expressed by Equation (2) below. In
Equation (2), N.sub.RB.sup.DL refers to the number of total
resource blocks corresponding to the downlink system bandwidth, and
N.sub.sc.sup.RB refers to the number of subcarriers in one resource
block. The k.sup.th subcarrier defined by Equation (2) corresponds
to a normal subframe serving as a positioning subframe.
k=6m+(.nu.+.nu..sub.shift)mod 6
m=0, 1, . . . 2N.sub.RB.sup.DL-1 (2)
[0049] In equation (2), .nu. corresponds to a value defining
positions of the different positioning reference signals in the
frequency domain as described above, and .nu..sub.shift corresponds
to a shift variance by which the positions of the subcarriers, in
which the PRSs are formed in each symbol according to the SFN and
the cell-specific information, are equally cyclic-shifted. Further,
.nu..sub.shift may have a value corresponding to a remainder after
dividing a value generated by a function of the SFN and the
cell-specific information by 6, which is a total possible frequency
shift value. Especially, .nu..sub.shift may be obtained through a
computation process in which one or more pseudo-random sequence
values are first obtained by a function of positioning subframe
numbers from a pseudo-random sequence created with the
cell-specific information, such as PCI (Physical Cell Identity), as
an initial value, the obtained pseudo-random sequence values are
multiplied by a constant and are then summed, and then the sum is
divided by 6, which is a total possible frequency shift value, so
that the remainder of the division is obtained as .nu..sub.shift.
This computation process can be expressed by Equation (3)
below.
v shift = f ( n subframe , N cell ID ) .fwdarw. v shift = ( i a i c
( f ( n subframe , i ) ) ) mod 6 ( 3 ) ##EQU00003##
[0050] In Equation (3), N.sub.Cell.sup.ID indicates a PCI (Physical
Cell ID) and 0.ltoreq.N.sub.Cell.sup.ID<504; .alpha. indicates a
constant; C(i) indicates a pseudo-random sequence; and C.sub.init
is an initial value of C, which is initialized at every subframe
for positioning, wherein C.sub.init=N.sub.Cell.sup.ID.
[0051] The processes as described above can be expressed using
equations as follows. That is, a PRS (positioning reference signal)
sequence f.sub.l,n.sub.S(m) mapped to a complex-valued modulation
symbol .alpha..sub.k,l.sup.(p) obtained through a modulation into a
complex value, which is used as a positioning reference symbol for
an antenna port p at the n.sub.s.sup.th slot, can be expressed by
Equation (4) below.
a k , l ( p ) = r l , n s ( m ' ) k = 6 m + ( v + v shift ) mod 6 l
= N symb DL - i for i = 1 , 2 , 4 , , 4 + ( n 5 mod 2 ) + N CP m =
0 , 1 , , 2 N RB DL - 1 m t = m + N RB max , DL - N RB DL ( 4 ) N
CP = { 1 for normal CP 0 for extended CP ##EQU00004##
[0052] From Equation (4), l can be defined by
l = { 2 , 3 , 5 , 6 if n 5 mod 2 = 0 and N CP = 1 1 , 2 , 3 , 5 , 6
if n 5 mod 2 = 1 and N CP = 1 2 , 4 , 5 if n 5 mod 2 = 0 and N CP =
0 1 , 2 , 4 , 5 if n 5 mod 2 = 1 and N CP = 0. ##EQU00005##
[0053] In Equation (4), .nu. and .nu..sub.shift, which are values
for defining positions of the different positioning reference
signals in the frequency domain, can be defined by Equation (5)
below. Further, .nu..sub.shift corresponds to a value specified to
the cell-specific information and the positioning subframe
number.
v = 5 - l + N CP v shift = f ( n subframe , N cell ID ) .fwdarw. v
shift = ( i a i c ( f ( n subframe , i ) ) ) mod 6 ( 5 )
##EQU00006##
[0054] In Equation (5), n.sub.subframe refers to a positioning
subframe number, and C.sub.init indicates an initial value of C and
is initialized at every subframe for positioning, wherein
C.sub.init=N.sub.Cell.sup.ID in a pseudo-random sequence C(i).
[0055] FIG. 4 illustrates a transmission apparatus to generate and
transmit a PRS pattern according to an exemplary embodiment of the
present invention.
[0056] Referring to FIG. 4, the transmission apparatus 400 to
generate and transmit a PRS (Positioning Reference Signal) pattern
includes a sequence generator 410 and a PRS resource allocator 420.
The sequence generator 410 generates a PRS sequence according to
the above-described manner. The PRS resource allocator 420
allocates PRSs formed according to the PRS sequence generated by
the sequence generator 410 to resource elements according to a PRS
pattern and a muting pattern, which will be described below in more
detail. Then, the PRSs allocated to the resource elements are
multiplexed with a BS transmission frame. As used herein, the PRS
pattern refers to a transmission pattern of PRSs defined in a
single subframe, and the muting pattern refers to a PRS
transmission pattern based on each subframe, which includes a
definition for the PRS pattern.
[0057] In resource allocation for the PRS, the PRS resource
allocator 420 allocates resources to OFDM symbols (x-axis) and
subcarriers (y-axis) according to a rule, and multiplexes the
resources with the BS transmission frame at a frame time.
[0058] Hereinafter, a signal generation structure of a downlink
physical channel of a wireless communication system, to which
embodiments of the present invention are applied, will be described
with reference to FIG. 4. In the signal generation structure of a
downlink physical channel of a wireless communication system
according to exemplary embodiments of the present invention, other
elements may be omitted or added, or may be changed to or replaced
by still other elements.
[0059] In the downlink, bits input in the form of code words after
being channel-coded are scrambled by a scrambler, and are then
input to a modulation mapper. The modulation mapper modulates the
scrambled bits into complex modulation symbols, and a layer mapper
maps the complex modulation symbols to one or more transmission
layers. Thereafter, a precoder precodes the complex modulation
symbols on each transmission channel of an antenna port. Then, a
resource element mapper maps the complex modulation symbols of each
antenna port to corresponding resource elements. The PRS resource
allocator 420 generates a positioning reference signal pattern from
the sequence generated by the sequence generator 410 and maps
positioning reference signals according to the positioning
reference signal pattern.
[0060] That is, in the wireless communication system 400, the PRS
resource allocator 420 allocates the PRSs, which have been
generated according to a particular positioning reference signal
sequence and then processed by at least one device, to resource
elements corresponding to resources, at which particular OFDM
symbols (time axis) and subcarriers (frequency axis) are located,
according to the positioning reference signal pattern formed
according to a sequence, and then multiplexes them with the BS
transmission frame at a predetermined frame time.
[0061] Existing reference signals (RSs), control signals, and data
input from the precoder are allocated to resource elements
corresponding to resources, at which particular OFDM symbols (time
axis) and subcarriers (frequency axis) are located by the resource
element mapper. The resource element mapper includes a device for
performing a special function (for example, for forming and mapping
a positioning reference signal pattern) added in order to allocate
the PRSs to the resource elements, which corresponds to a PRS
mapping unit.
[0062] Thereafter, an OFDM signal generator generates a complex
time domain OFDM signal for each antenna. This complex time domain
OFDM signal is transmitted through an antenna port.
[0063] As illustrated in FIG. 2 and FIG. 3, the positioning
reference signal pattern for a subframe and one Resource Block in
the frequency axis is repeatedly copied and transmitted with the
same pattern for the system bandwidth for the positioning reference
signals in the frequency axis. In the time axis, the positioning
reference signal pattern is transmitted through consecutive 1, 2,
4, or 6 subframes with a particular offset at a period of, for
example, 160 ms (160subframe), 320 ms (320subframe), 640 ms
(640subframe) or 1280 ms (1280subframe). The bandwidth for
positioning reference signals in the frequency axis, and the period
and the offset of subframes for transmission of positioning
reference signals, and the number of consecutive subframes for
transmission of positioning reference signals in the time axis in
each BS 20 are controlled by a high layer, and this information is
transmitted to each UE 10 through a Radio Resource Controller
(RRC).
[0064] Herein, a cell specific subframe configuration period,
T.sub.PRS, for transmission of positioning reference signals may be
160, 320, 640, or 1280 subframes, and a cell specific subframe
offset may be [I.sub.PRS], [I.sub.PRS-160], [I.sub.PRS-480],
[I.sub.PRS-1120]. The PRS configuration index I.sub.PRS can be
determined by a high layer.
[0065] The positioning reference signals used for measurement of a
user's position can be transmitted during a time. For measuring a
more exact position, during a specified given time, either a time
varying pattern transmission or a time non-varying pattern
transmission may be performed. For example, if one subframe is the
minimum unit for transmitting the positioning reference signal, the
positioning reference signals may be transmitted over 2, 3, 4 . . .
N subframes. At this time, the same positioning reference signal
pattern is transmitted in each subframe in the case of time
non-varying pattern transmission, and different positioning
reference signal patterns are transmitted in the case of time
varying pattern transmission.
[0066] Specifically, when the PRS patterns are cyclic-shifted along
the frequency axis as shown in FIG. 2 and FIG. 3, the number of PRS
patterns determinable from each other is six. Then, the BSs 20 can
be divided into a total of six groups and the PRSs can be
transmitted with six different PRS patterns. However, when taking
the BSs 20 up to tier 2 into consideration based on the UE 10,
there are BSs 20 corresponding to 19 cell sites or 57 cells (based
on an assumption that only the BSs 20 up to tier 2 are BSs, from
which the PRSs can be actually received, since PRSs transmitted
from BSs above tier 2 are weak when they are received by a
corresponding UE). Therefore, only the six PRS patterns are
insufficient for transmission of PRSs having different patterns for
every BS up to tier 2 and cannot avoid an existence of multiple BSs
20 having the same PRS pattern, which may cause performance
degradation due to an interference between BSs in PRS
transmission.
[0067] In the case of transmitting PRSs during more than a minimum
time unit, that is, in the case of transmitting PRSs during more
than one subframe as in the example described above, it is possible
to either transmit the PRSs over every predetermined N subframe or
mute transmission of the PRSs by a particular BS 20 in order to
improve the performance by reducing an interference between BSs in
the PRS transmission.
[0068] FIG. 5 illustrates a method of transmitting PRSs in muting
patterns for N and K according to an exemplary embodiment of the
present invention
[0069] Referring to FIG. 5, in transmitting positioning reference
signals during 0 or N-1 subframes, the subframes are divided into
"Transmit" subframe intervals, in which positioning reference
signal are transmitted, and "Mute" subframe intervals, in which
positioning reference signals are not transmitted.
[0070] Further, the time for transmission of PRSs by each BS is
divided once more subframe by subframe, so as to further identify
BSs transmitting the PRSs with the same PRS pattern. As a result,
in the case of considering regional characteristics of BSs and
effects of interference between BSs, it is possible to achieve a
better performance than the method of transmitting positioning
reference signals in all subframes.
[0071] Aspects of the present invention provide a transmission
method according to a muting pattern determined by using a time
offset (cyclic shift), in which the PRS is transmitted in a
particular subframe and is not transmitted in another particular
subframe, in order to achieve measurement of a more exact position
of a UE.
[0072] Aspects of the present invention provide a method for
constructing and transmitting a Positioning Reference Signal (PRS),
which is a reference signal or pilot signal for location estimation
of a UE, in a resource allocation structure for data transmission
in a wireless communication system.
[0073] Aspects of the present invention provide a method for
transmitting cell-specific numbers and PRSs having excellent
performance, for more exact location estimation required by the
development of communication, such as increasing moving speed of
the UE, change of interference between BSs, and increasing
complexity.
[0074] Aspects of the present invention provide a muting method in
which the PRS is transmitted in a particular subframe and is not
transmitted in another particular subframe. Further, aspects of the
present invention provide a muting method, which can reduce the
interference between PRSs transmitted to BSs, can be constructed in
a simple and equal manner in all considerable transmission methods,
and requires less assistant data from a higher layer in order to
improve the exactness in measurement of a position of a UE.
[0075] As described above, the positioning reference signals are
transmitted repeatedly with a specific period. For example, the
positioning reference signals are transmitted in consecutive 1, 2,
4, or 6 subframes with the period of, for example, 160 ms (160
subframes), 320 ms (320 subframes), 640 ms (640 subframes) or 1280
ms (1280 subframes). At this time, the bandwidth for positioning
reference signals from each BS 20, the period of subframes in the
time axis, offset, and the number of consecutive subframes being
transmitted are controlled by a high layer, and such information is
transmitted to each UE 10 by the RRC (Radio Resource Controller).
Such information is included in Tables 1 and 2.
[0076] Table 1 shows assistance data associated with a serving
cell.
[0077] As noted from Table 1, the assistance data related to the
serving cell includes bandwidth for positioning reference signals,
positioning reference signals configuration index, and number of
consecutive downlink subframes, N.sub.PRS.
TABLE-US-00001 TABLE 1 Information Size (bits) Explanation
Bandwidth for [X] The bandwidth that is used to positioning conFIG.
the positioning reference reference signals signals on.
N.sub.RB.sup.PRS Positioning [12] ConFIG.s the periodicity and
reference signals offset of the subframes with configuration Index
positioning reference signals. I.sub.PRS For example, periodicities
of 160, 320, 640, or 1280 subframes Number of [2] ConFIG.s number
of consecutive consecutive downlink subframes with downlink
subframes positioning reference signals. N.sub.PRS For example, 1,
2, 4, or 6 consecutive subframes
[0078] Table 2 also shows assistance data associated with measured
cells as assistant data for positioning.
[0079] As noted from Table 2, the assistant data related to the
measured cell includes PCI, Timing offset, normal or extended CP,
Antenna port configuration, Slot number offset, and Muting
offset.
[0080] Aspects of the present invention additionally employ a new
Muting Offset (cyclic shift), so that a user can see information
regarding Muting Offset of the measured cell.
TABLE-US-00002 TABLE 2 Size (bits) Information per cell Explanation
PCI N.sub.ID.sup.cell 9 The PCI for each cell that the UE should
measure on. Timing offset [X] The transmit timing offset between
the serving cell and the measured cell. Normal or extended 1 bit
per 1 bit per measured cell, indicating CP N.sub.CP measured
positioning reference signals with cell, or 1 bit normal or
extended cyclic prefix. 1 bit, indicating that all measured cells
have the same length of the CP as the serving cell Antenna port 1
bit per 1 bit per measured cell, indicating configuration measured
1 (or 2) antenna port(s) or 4 cell, or 1 bit antenna ports for cell
specific reference signals 1 bit, indicating that all measured
cells transmits cell specific reference signals on the "same"
antenna port(s) as the serving cell. Here, 1 and 2 antenna ports
are regarded as the "same". Slot number offset 5 bits per 5 bits
per measured cell, n.sub.s measured indicating the slot number
offset cell, or 1 bit between the serving cell and the measured
cell. 1 bit, indicating that all measured cells has the same slot
timing as the serving cell. Muting offset 1 to 3 bit per 1 to 3
bits per measured cell, (cyclic shift) n.sub.m measured indicating
the muting offset (cyclic cell shift) between the serving cell and
the measured cell or muting offset pattern group
[0081] Aspects of the present invention provide a muting offset
(cyclic shift) n.sub.m as shown in Table 2.
[0082] The muting offset may have one to three bits per measured
cell, and indicates how many bits a cell group has as the muting
offset. That is to say, the muting offset refers to a muting offset
(cyclic shift) between the serving cell and a measured cell or a
muting offset pattern group.
[0083] Hereinafter, values, which the muting offset may have, will
be described with reference to Tables 3 to 5. NPRS in Tables 3 to 5
corresponds to the number of consecutive downlink subframes having
positioning reference signals.
[0084] Referring to FIG. 6, regarding N (for example, N=1, 2, 4, or
6) consecutive subframes assigned in order to transmit positioning
reference signals with a period (for example, 160 ms, 320 ms, 640
ms, or 1280 ms; one subframe corresponds to 1 ms), each BS (or cell
group) 20 transmits positioning reference signals in K (i.e., 2)
subframes among the N subframes, while muting the (N-K) subframes,
i.e., (N-2) subframes, without transmitting any positioning
reference signal in the (N-K) subframes.
[0085] The cell groups are divided into (N+1) cell groups, and the
positioning reference signals are transmitted with different muting
patterns according to the (N+1) cell groups. For example, cell
group #1 is mute without transmission of a positioning reference
signal in all of the N subframes allocated for the transmission of
the positioning reference signals during a period (or, in other
words, transmits the positioning reference signals with a power of
0). Cell group #2 transmits positioning reference signals in the
first and second subframes among the N subframes, while muting
without transmission of a positioning reference signal in the
remaining subframes. Cell group #3 transmits positioning reference
signals in the second and third subframes among the N subframes
allocated for transmission of the positioning reference signals
during the period with a muting offset of 1, while muting without
transmission of a positioning reference signal in the remaining
subframes. In the same way, cell group #N transmits positioning
reference signals in the (N-1)th and Nth subframes among the N
subframes allocated for transmission of the positioning reference
signals during the period with a muting offset of (N-2), while
muting without transmission of a positioning reference signal in
the remaining subframes. Finally, cell group #(N+1) transmits
positioning reference signals in the Nth and first subframes among
the N subframes allocated for transmission of the positioning
reference signals during the period with a muting offset of (N-1),
while muting without transmission of a positioning reference signal
in the remaining subframes. As noted from the final cell group,
i.e., cell group #(N+1), the muting offset returns to the first
subframe after the cyclic-shifting through the N subframes
allocated for transmission of the PRSs.
TABLE-US-00003 TABLE 3 Value Offset (Cyclic shift) 000 Persistent
muting cell group 001 0 subframe 010 1 subframe 011 2 subframe 100
3 subframe 101 4 subframe 110 5 subframe 111 reserved
[0086] Table 3 shows values of the muting offset determined by
three bits. The three bit muting offset can express up to N
N.sub.PRS=6 in the muting pattern as shown in FIG. 6. That is to
say, because of N=6 and K=2 (PRSs are transmitted by two subframes
among the six subframes), the cell groups are divided into a total
of seven cell groups, which can be identified in sequence by "000"
to "110", i.e., by the three bits.
[0087] Since the muting offset values as determined by the three
bits, when N.sub.PRS=6, seven muting patterns exist and the number
of BSs 20 determinable by time and frequency are 6 according to
different positioning reference signal patterns. Therefore, it is
possible to identify 42 BSs.
[0088] In addition, the number, M, corresponds to the number of all
the cell groups including the persistent muting cell groups. The
persistent muting cell groups mute without transmission of PRSs in
the N subframes allocated for transmission of the positioning
reference signals during a period. The number M of cell groups, the
number of cells in each cell group, and the number K, which
indicates the length of the consecutive subframes transmitting the
PRSs without muting among the entire N subframes allocated for
transmission of the PRSs, can be determined by the BS 20 or core
network.
[0089] The above-described method can identify more cell groups and
generate more muting patterns. The above-described method
determines the muting offset by three bits, as shown in Table 3.
Further, the muting offset increases by the value of "1" and both
cell group #i (i indicates a natural number smaller than (N+1)) and
cell group #(i+1) transmit PRSs in the i.sup.th subframe. For
example, both cell group #2 and cell group #3 transmit PRSs in the
second subframe.
TABLE-US-00004 TABLE 4 Value Offset 00 Persistent muting cell group
01 0 subframe 10 N.sub.PRS/2 subframe 11 reserved
[0090] Table 4 shows a method for expressing the muting offset in
two bits. Referring to Table 4, the muting offset value of "00"
corresponds to a persistent muting cell group, which is mute
without transmission of a positioning reference signal in all the N
subframes allocated for the transmission of the positioning
reference signals during a period. The muting offset value of "01"
corresponds to a cell group, which has a muting offset of 0 and
transmits positioning reference signals in K subframes of the front
side among N subframes, while muting the remaining (N-K) subframes
after the K subframes without transmitting any positioning
reference signal in the remaining (N-K) subframes. The muting
offset value of "10" corresponds to a cell group having a muting
offset of NPRS/2 and that transmits positioning reference signals
in K subframes from the (NPRS/2)th subframe among N subframes,
while muting the remaining (N-K) subframes without transmitting any
positioning reference signal in the (N-K) subframes.
[0091] As described above, in this method, the cell groups are
bundled into three groups and the values for the muting offset are
expressed by two bits. Therefore, it is possible to decrease the
information bits for expressing the muting offset and to decrease
any interference from another cell group.
[0092] Since the cell groups are bundled into three groups by the
muting offset and the number of BSs 20 identifiable according to
the time and frequency is six according to the different PRS
patterns, it is possible to identify a total of 18 BSs 20.
[0093] Hereinafter, muting patterns, in which the muting offset is
expressed by two bits and the cell groups are bundled into three
groups as shown in Table 4 when the number NPRS of downlink
subframes for the positioning reference signals are 2, 4, and 6,
respectively, will be described with reference to FIG. 7. FIG. 8,
and FIG. 9.
[0094] FIG. 7 illustrates muting patterns, in which the cell groups
are bundled into three cell groups, and the number NPRS of downlink
subframes for the positioning reference signals is 2.
[0095] Referring to FIG. 7, the number NPRS of downlink subframes
for the positioning reference signals is 2, and the number K of
consecutive PRS subframes for transmitting the positioning
reference signals is 1.
[0096] From among two consecutive subframes allocated for
transmitting positioning reference signals with a period (for
example, 160 ms, 320 ms, 640 ms, or 1280 ms; one subframe
corresponds to 1 ms), some BS groups transmit PRSs in one subframe
while muting the remaining subframe without transmission of PRSs
therein.
[0097] Cell group #1 is mute without transmission of a positioning
reference signal in both of the two subframes allocated for the
transmission of the positioning reference signals during a period
(or, in other words, transmits the positioning reference signals
with a power of 0). Cell group #2 has a muting offset of 0 and
transmits positioning reference signals in the first subframe
(subframe #0) among the two subframes allocated for the
transmission of the positioning reference signals during the
period, while muting without transmission of a positioning
reference signal in the remaining subframe. Cell group #3 has a
muting offset of NPRS/2 (=2/2=1) and transmits positioning
reference signals in the second subframe (subframe #1) among the
two subframes allocated for the transmission of the positioning
reference signals during the period, while muting without
transmission of a positioning reference signal in the remaining
subframes.
[0098] The number M of cell groups, the number of cells in each
cell group, and the length K of the consecutive PRS subframes
allocated for transmission of the PRSs during the period can be
selected by the BS 20 or core network.
[0099] FIG. 8 illustrates muting patterns in which the cell groups
are bundled into three cell groups, and the number NPRS of downlink
subframes for the positioning reference signals is 4.
[0100] Referring to FIG. 8, the number NPRS of downlink subframes
for the positioning reference signals is 4, and the number K of
consecutive PRS subframes for transmitting the positioning
reference signals is 2.
[0101] From among four consecutive subframes allocated for
transmitting positioning reference signals with a period (for
example, 160 ms, 320 ms, 640 ms, or 1280 ms; one subframe
corresponds to 1 ms), some BS groups transmit PRSs in two subframes
while muting the remaining subframes without transmission of PRSs
therein.
[0102] Cell group #1 is persistently mute without transmission of a
positioning reference signal in all of the four subframes allocated
for the transmission of the positioning reference signals during a
period (or, for example, transmits the positioning reference
signals with a power of 0). Cell group #2 has a muting offset of 0
and transmits positioning reference signals in the first and second
subframes (subframe #0 and subframe #1) among the four subframes
allocated for the transmission of the positioning reference signals
during a predetermined period, while muting without transmission of
a positioning reference signal in the remaining subframes. Cell
group #3 has a muting offset of NPRS/2 (=4/2=2) and transmits
positioning reference signals in the third and fourth subframes
(subframe #2 and subframe #3) among the four subframes allocated
for the transmission of the positioning reference signals during a
predetermined period, while muting without transmission of a
positioning reference signal in the remaining subframes.
[0103] The number of cell groups, the number of cells in each cell
group, and the length of the consecutive PRS subframes allocated
for transmission of the PRSs during the period can be selected by
the BS 20 or core network.
[0104] FIG. 9 illustrates muting patterns in which the cell groups
are bundled into three cell groups, and the number NPRS of downlink
subframes for the positioning reference signals is 6.
[0105] Referring to FIG. 9, the number NPRS of downlink subframes
for the positioning reference signals is 6, and the number K of
consecutive PRS subframes for transmitting the positioning
reference signals is 3.
[0106] From among six consecutive subframes allocated for
transmitting positioning reference signals with a period (for
example, 160 ms, 320 ms, 640 ms, or 1280 ms; one subframe
corresponds to 1 ms), some BS groups transmit PRSs in three
subframes while muting the remaining three subframes without
transmission of PRSs therein.
[0107] Cell group #1 persistently mutes without transmission of a
positioning reference signal in all of the six subframes allocated
for the transmission of the positioning reference signals during a
period (or, for example, transmits the positioning reference
signals with a power of 0). Cell group #2 has a muting offset of 0
and transmits positioning reference signals in the first, second,
and third subframes among the six subframes allocated for the
transmission of the positioning reference signals during the
period, while muting without transmission of a positioning
reference signal in the remaining subframes. Cell group #3 has a
muting offset of NPRS/2 (=6/2=3) and transmits positioning
reference signals in the fourth, fifth, and sixth subframes among
the six subframes allocated for the transmission of the positioning
reference signals during a predetermined period, while muting
without transmission of a positioning reference signal in the
remaining subframes.
[0108] The number of cell groups, the number of cells in each cell
group, and the length of the consecutive PRS subframes allocated
for transmission of the PRSs during the period can be selected by
the BS 20 or core network.
[0109] FIG. 10 illustrates muting patterns, in which the cell
groups are bundled into three cell groups, and the number NPRS of
downlink subframes for the positioning reference signals is 4.
[0110] Referring to FIG. 10, the number NPRS of downlink subframes
for the positioning reference signals is 4, and the number K of
consecutive PRS subframes for transmitting the positioning
reference signals is 2.
[0111] From among four consecutive subframes allocated for
transmitting positioning reference signals with a period (for
example, 160 ms, 320 ms, 640 ms, or 1280 ms; one subframe
corresponds to 1 ms), some BS groups transmit PRSs in two subframes
while muting the remaining subframes without transmission of PRSs
therein.
[0112] Cell group #1 persistently transmits positioning reference
signals in all of the four subframes allocated for the transmission
of the positioning reference signals during a period. Cell group #2
has a muting offset of 0 and transmits positioning reference
signals in the first and second subframes (subframe #0 and subframe
#1) among the four subframes allocated for the transmission of the
positioning reference signals during the period, while muting
without transmission of a positioning reference signal in the
remaining subframes (subframe #2 and subframe #3). Cell group #3
has a muting offset of NPRS/2 (=4/2=2) and transmits positioning
reference signals in the third and fourth subframes (subframe #2
and subframe #3) among the four subframes allocated for the
transmission of the positioning reference signals during the
period, while muting without transmission of a positioning
reference signal in the remaining subframes (subframe #0 and
subframe #1).
[0113] The number of cell groups, the number of cells in each cell
group, and the length of the consecutive PRS subframes allocated
for transmission of the PRSs during the period can be selected by
the BS 20 or core network.
TABLE-US-00005 TABLE 5 Value Offset 0 0 subframe 1 N.sub.PRS/2
subframe
[0114] Table 5 is a table expressing the muting offset by one bit
according to a method for transmitting information of persistent
muting cells, which are mute without transmission of PRSs in the N
subframes allocated for transmission of the positioning reference
signals during a period.
[0115] The information bit is set to have a variable length. That
is, the persistent muting cells, which are mute without
transmission of PRSs in the N subframes allocated for transmission
of the positioning reference signals during the period, can be
identified by removing the muting offset (cyclic shift) field since
the muting offset information for the persistent muting cells is
not transmitted. Then, as shown in Table 5, it is possible to
discriminate two cell groups each including a muting offset field
by only one bit.
[0116] Referring to Table 5, when there is no muting offset field,
it implies a muting cell group, which is mute without transmission
of PRSs (or transmits the PRSs with a power of 0) in the N
subframes allocated for transmission of the positioning reference
signals during a period. The muting offset value of "0" corresponds
to a cell group, which has a muting offset of 0 and transmits
positioning reference signals in K subframes of the front side
among N subframes, while muting the remaining (N-K) subframes after
the K subframes without transmitting any positioning reference
signal in the (N-K) subframes. The muting offset value of "1"
corresponds to a cell group that has a muting offset of NPRS/2 and
transmits positioning reference signals in K subframes from the
(NPRS/2)th subframe among the N subframes, while muting the
remaining (N-K) subframes without transmitting any positioning
reference signal in the (N-K) subframes.
[0117] In the method of Table 5 described above, cells are bundled
into three cell groups and the muting offset can be expressed by a
value of one bit. Therefore, it is possible to decrease the
information bits for expressing the muting offset and to decrease
any interference from another cell group.
[0118] Hereinafter, an operation of a UE according to an exemplary
embodiment of the present invention will be described with
reference to FIG. 11 and FIG. 12, and Table 4.
[0119] FIG. 11 illustrates an arrangement of BSs (cells) divided
into three groups according to the muting pattern for transmission
of PRSs based, and FIG. 12 is a flowchart illustrating a method of
positioning of a UE according to an exemplary embodiment of the
present invention.
[0120] Referring to FIG. 12, first, a UE 10 for which a positioning
thereof is to be determined receives assistant data or information
as shown in Tables 1 and 2 from a serving cell (operation S1210).
In Table 1, the UE 10 can obtain the bandwidth of PRSs from
N.sub.RB.sup.PRS and the period and offset information of the PRSs
from I.sub.PRS wherein the offset information herein is different
from the muting offset and indicates an offset for transmission of
the PRSs in each period. Further, the UE 10 can obtain the number
of downlink subframes allocated for transmission of the PRSs from
N.sub.PRS.
[0121] As described above, one, two, four, or six sub-frames are
allocated as consecutive subframes for transmitting PRSs. In
operation S1220, the UE 10 receives assistant data or information
related to measured cells indicated in Table 2. In the received
assistant data related to a measured cell, the UE 10 obtains a cell
identifier (ID) of the measured cell from PCI N.sub.ID.sup.cell.
Although the other parameters may also be necessary for the
positioning, they are not described in detail since they have no
direct relation to the present exemplary embodiment. Finally, the
UE 10 can obtain muting offset information of the measured cell
from the muting offset (cyclic shift) n.sub.m. Upon obtaining all
the information of Table 2, the UE 10 can determine the muting cell
groups to which each of the measured cells belongs, and determine
the muting pattern by which the PRSs are transmitted.
[0122] When the muting offset has a value of two bits as in Table
4, it is possible to arrange an environment in which information
bits are constructed as shown in Table 6 below.
TABLE-US-00006 TABLE 6 PCI N.sub.ID.sup.cell Muting (measured
offset (cyclic cell) shift) n.sub.m Cell group 1 00 Cell group 1 2
01 Cell group 2 3 10 Cell group 3 4 00 Cell group 1 5 01 Cell group
2 6 10 Cell group 3 7 01 Cell group 2 8 00 Cell group 1 9 10 Cell
group 3 10 00 Cell group 1 11 01 Cell group 2 12 10 Cell group 3 13
10 Cell group 3 14 01 Cell group 2 15 00 Cell group 1 16 01 Cell
group 2 17 10 Cell group 3 18 00 Cell group 1 19 00 Cell group 1 20
01 Cell group 2 21 10 Cell group 3
[0123] The assistant data in Table 6 corresponds to information,
which is given to a UE 10 for which a positioning thereof is
determined in a cell deployment environment as shown in FIG. 11. As
noted from Table 6, the cell group division according to the muting
pattern enables an allocation and arrangement of the cells or BSs,
which can reduce the occurrence of interference in the BS 20 or
core network.
[0124] Upon receiving the information, the UE 10 can identify the
muting cell groups of the measured cells including the serving cell
and identify the muting pattern of each cell (operation S1230).
After identifying the muting pattern of each cell, the UE 10 can
decode the PRSs and use them for the positioning according to a
general positioning method (operation S1240).
[0125] The UE 10 receives PRSs having different PRS patterns and
different muting patterns from at least three different BSs 20 and
decodes the PRSs. For example, as shown in FIG. 11, the UE 10
receives PRSs having different PRS patterns and different muting
patterns from cell #1, cell #2, and cell #3 belonging to cell group
#1, cell group #2, and cell group #3, and decodes the PRSs.
[0126] According to the OTDOA (Observed Time Difference of Arrival)
method, the UE 10 estimates the distance from each BS 20 by using
the received relative arrival times from the at least three BSs 20.
Then, the UE 10 estimates the position of itself through a
triangulation (operation S1250).
[0127] FIG. 13 is a block diagram illustrating a signal receiving
apparatus of a UE according to an exemplary embodiment of the
present invention.
[0128] The signal receiving apparatus 1300 of a UE 10 includes a
reception unit 1310, a decoding unit 1320, and a control unit
1330.
[0129] The reception unit 1310 receives assistant data or
information of a serving cell as shown in Tables 1 and 2 and
assistant data or information of measured cells as shown in Table 2
from the serving cell. Then, from the received assistant data or
information of the serving cell and measured cells, the reception
unit 1310 can identify the muting cell groups, to which the serving
cell and measured cells belong, and can identify the muting pattern
of each cell. The reception unit 1310 receives PRSs having
different PRS patterns and different muting patterns from three or
more different BSs 20.
[0130] After identification of the muting pattern of each cell, the
decoding unit 1320 decodes the PRSs according to a general
positioning method. The decoding unit 1320 decodes the PRSs having
different PRS patterns and different muting patterns, which have
been received from three or more different BSs 20 by the reception
unit 1310.
[0131] According to the OTDOA (Observed Time Difference of Arrival)
method, the control unit 1330 estimates the distance from each BS
20 by using the relative arrival times of the PRSs from the three
or more different BSs 20, which have been decoded by the decoding
unit 1320. Then, the control unit 1330 estimates the position of
the UE 10 through a triangulation
[0132] Hereinafter, a positioning operation of the signal receiving
apparatus 1300 of the UE 10 will be described.
[0133] The reception unit 1310 converts signals received through
antenna ports to complex time domain signals. Further, the
reception unit 1310 extracts PRSs of particular resource elements
from the received signals by using the PRS pattern and muting
pattern. The decoding unit 1320 decodes the extracted PRSs. The
control unit 1330 measures distances from BSs 20 by using relative
arrival times from the BSs 20 through the decoded PRSs. At this
time, instead of calculating, by the control unit 1330 itself, the
distances from BSs 20 by using the relative arrival times from the
BSs 20, the control unit 1330 may transmit the relative arrival
times to the BSs 20 so that the BSs 20 may calculate the distances.
Then, since the distances from at least three BSs are measured, it
is possible to calculate the position of the UE 10.
[0134] The signal receiving apparatus 1300 described above is a
counterpart of the transmission apparatus 400 of the wireless
communication system described above with reference to FIG. 4 and
receives a signal transmitted from the transmission apparatus 400.
The signal receiving apparatus 1300 includes elements for a signal
processing opposite to the signal processing by the transmission
apparatus 400. Therefore, it should be understood that elements of
the signal receiving apparatus 1300 not described in detail can be
replaced by corresponding elements for a signal processing opposite
to the signal processing by the transmission apparatus 400,
respectively.
[0135] Meanwhile, allocation of muting cell groups as shown in
Table 6 may be performed either to decrease interference in the BS
20 or core network as described above or according to groups
obtained by dividing the cells through a modulo operation of the
PCIs (Physical Cell IDs).
[0136] As described above with reference to Tables 3 to 6, it is
possible to define the muting offset n.sub.m, by tabular bit values
corresponding to specific cases, respectively. However, a method of
commonly defining the muting offset in the same manner for all the
cases shown in FIGS. 6 to 10 will now be described.
[0137] From among M cell groups, a muting offset of the i.sup.th
cell group can be defined by Equation (6) below.
Muting offset=(i-1).left brkt-bot.N.sub.PRS/(M-1).right brkt-bot.
for 1.ltoreq.i.ltoreq.M-1 (6)
[0138] In Equation (6), a case in which i=0 corresponds to a
persistent muting cell group, which mutes without transmitting a
PRS in all N subframes allocated for transmission of PRSs during a
period, or a persistent transmitting cell group, which transmits
PRSs in all N subframes.
[0139] At this time, assistant data for an additionally given
muting offset n.sub.m has a size of a total of .left
brkt-top.log.sub.2 M.right brkt-bot. bits. Further, from among
2.sup..left brkt-top.log.sup.2.sup.M.right brkt-bot. values, which
can be expressed by the .left brkt-top.log.sub.2 M.right brkt-bot.
bits, M binary values from 0 to (M-1) are used while the other
values are reserved. At this time, each of the M binary values
expresses the ith cell group.
[0140] For example, in FIG. 2, if NPRS=6, M=7. Then, cell group #i
is defined by values of i from 0 to 6, and assistance data for the
muting offset n.sub.m can be expressed by three bit values as shown
in Table 7. The muting offset values according to the values of i
in Table 7 can be determined from Equation (6). As shown, Table 7
corresponds to a general expression of Table 3.
TABLE-US-00007 TABLE 7 Value Cell group i Offset (Cyclic shift) 000
i = 0 Persistent muting cell group 001 i = 1 Offset = 0 subframe
010 i = 2 Offset = 1 subframe 011 i = 3 Offset = 2 subframe 100 i =
4 Offset = 3 subframe 101 i = 5 Offset = 4 subframe 110 i = 6
Offset = 5 subframe 111 Reserved
[0141] The values, which the muting offset may have, are expressed
by three bits. Therefore, when NPRS=6, it is possible to identify
42 base stations since there are seven muting patterns and the
number of base stations determinable by time and frequency are 6
according to different positioning reference signal patterns.
[0142] Further, in the example shown in FIGS. 7 to 9, NPRS is 2 4,
or 6, and cell group #i is defined by a value of 0 to 2 when M=3.
Moreover, as shown in Table 8 below, assistance data for the muting
offset n.sub.m can be expressed by two bits. In table 8, the muting
offset values according to i can also be determined from Equation
(6). As shown, Table 8 serves as a general expression of Table
4.
TABLE-US-00008 TABLE 8 Value Cell group i Offset (Cyclic shift) 00
i = 0 Persistent muting (or transmitting) cell group 01 i = 1
Offset = 0 subframe 10 i = 2 Offset = .left
brkt-bot.N.sub.PRS/2.right brkt-bot. subframe 11 reserved
[0143] By calculating the muting offset by using Equation (6)
described above, it is possible to generally define the muting
offset in the same manner regardless of the number NPRS of
consecutive subframes allocated for the PRSs, the number M of all
cell groups, and the length K of consecutive PRS subframes used for
transmission without muting from among the NPRS consecutive
subframes, and it is unnecessary to separately arrange a table for
defining the muting offset for each case.
[0144] In the above-described methods, a persistent transmitting
cell group transmitting PRSs may be taken into consideration
instead of the persistent muting cell group.
[0145] By a method of transmitting PRSs using a more effective and
efficient muting method according to aspects of the present
invention, it is possible to reduce interference, which may be
caused when multiple base stations 20 simultaneously transmit the
same PRS pattern as in the conventional muting method. In addition,
according to aspects of the present invention, it is possible to
employ a muting method in a simple and equal manner regardless of
subframes consecutively used during a period.
[0146] Further, in measuring the position of a UE 10 based on an
estimation of difference between arrival times of PRSs received and
demodulated by the UE 10, the muting method is effective in that it
decreases assistance data from a higher layer in order to identify
the muting pattern of PRSs transmitted from each BS 20. Therefore,
it is possible to use the transmitted PRSs more effectively and
efficiently.
[0147] Moreover, by implementing the muting pattern by using the
muting offset, it is possible to implement the muting pattern while
decreasing complexity thereof.
[0148] Although the embodiments described above are based on the
drawings, aspects of the present invention are not limited to the
described and illustrated embodiments. For example, in the muting
offset, in which positioning reference signals are transmitted in K
subframes among N subframes while the remaining (N-K) subframes are
mute without transmission of any positioning reference signal, the
K subframes may correspond to either subframes from the first
subframe to the Kth subframe with a time offset of a subframe, or
subframes from a subframe of another group with a time offset of
one subframe.
[0149] It will be apparent to those skilled in the art that various
modifications and variation can be made in the present invention
without departing from the spirit or scope of the invention. Thus,
it is intended that the present invention cover the modifications
and variations of this invention provided they come within the
scope of the appended claims and their equivalents.
* * * * *